Zama C1Q Nozzle Assembly Check valve replacement with pics

This has been my first experience with the notorious check valves found on newer carbs. I've been chasing this problem on a FS450 trimmer for a while but luckily it has been between cuts on Water Authority sites. Searching here didn't throw up much but these carbs are used on lots of blowers, trimmers and smaller saws. The carb is a Zama C1Q-S34H which is fixed jet with only what appears to be an air screw (reverse thread) for idle adjustment.Symptoms were hard starting, inconsistant idle which couldn't be adjusted and would run out of fuel with an inch still left in the tank. When operating the primer bulb you could keep pumping without it becoming full and air bubbles were visible in the bulb. At full throttle everything was fine but as soon as you let off it would often stop dead. New lines, primer bulb,fuel filter and a rebuild kit did nothing. The answer was eventually found on Zama's excellent website: http://www.zamacarb.com/tips.html.
Before you do anything to a Zama carb I would recommend reading all the Service Tips. Especially DO NOT BLOW COMPRESSED AIR THROUGH A CARB WITH CHECK VALVES. It seems you also have to be careful with aerosol carb cleaner if directed straight into the valve with an extension tube.
So here's how it went:



The jet at the bottom of the metering chamber is the main jet which Zama call the "Nozzle Assembly Check Valve". Stihl call it the "Valve Jet".
The hole in the middle, which is normally hidden by the metering lever leads to the idle circuit. To test both circuits use a piece of hose over the jet and blow with your mouth. If clear then try to suck back. If you can the check valve is defective. This is bad news on the idle circuit as it means a new carb but the main jet can be replaced. Zama do a special tool but I managed to use a cheap drill press and one of my extensive collection of broken drill bits. If you have adjusting screws remove the H before starting.



It took a fair bit of fiddling to get everthing lined up and more force than I expected to get the nozzle to move. Here it is out and the new one:



The new one went in a lot more easily:



A few minutes of reassembly and it fired right up. Ticks over fine now and is responsive to the LA screw.

Here is how the drill was set up. It was tricky to get the right angle but it turned out to be about 35 Degrees off horizontal. Yes the drill is rusty but it is pretty damp around these parts!



Here is the jet from a FS400 I did as well. This one was really hard to press out. You can see the deformation on the top.



It had a C1Q-S34C which wasn't listed in my IPL but the jet was a 0.52mm against the 0.53mm for the FS450. I made sure the metering lever wasn't high and figured slightly rich wouldn't hurt. As it turns out it runs fine.

Very good thread. Well done

It says I can't rep this thread :censored:

It sure deserves some!

This is good info to have here.

Good thread and pictures. I didn't realise how easy it was to push out the nozzle from inside the metering chamber. That's a clever way to use a drill press for removing and installing the nozzle. I'll use that method if I ever need to replace the nozzle. Rep sent.

Modifiedmark said:

It says I can't rep this thread :censored:

It sure deserves some!

Click to expand...

:agree2: I rep'd him for you.

+1

490, you used the bit as a screw extractor?

says i can't him him for a while.....someone get him......

nmurph said:

490, you used the bit as a screw extractor?

says i can't him him for a while.....someone get him......

Click to expand...

No the bit is in the chuck upside down and was static. I was using the drill to push the nozzle through into the bore of the carb. Didn't much fancy hitting a carb with a hammer and drift! Thankfully Zama don't install them into a blind hole.
Main reason for posting was that the symptoms I had seem to crop up all the time on posts here and on other forums but other than a new carb there weren't too many suggested fixes. Nozzles are about $3.50 in US and the same in pounds over here so a cheap fix.
Thanks for the rep everyone

Bad check valve causing flooding?

I know this is an old thread, but I'm having some problems with a Ryobi 10532 and am wondering if a defective check valve may be causing them.
At first the saw wouldn't pull fuel. Would fire with a shot of mix, but not keep running or pull fuel on it's own. Then I noticed when I pumped the primer bulb fuel tried to flow on BOTH directions, not just getting pulled thru the carb, that is, when you pushed the bulb in the fuel went one way, when you released it the fuel went the other. Also, the primer bulb would not pump up and get firm.
So I replaced the primer bulb.
After replacing the bulb, the fuel moves on the correct direction only (primer bulb sucks fuel thru carb) and the saw fires up immediately. But, it won't rev up and is flooding with fuel, as evidenced by fuel coming out the muffler. Runs at high idle speed.
I've pulled the carb apart, cleaned it out with carb cleaner, including cleaning the inlet needle, the needle jet and checked the needle height. The needle height looked OK to me, but I haven't done this a lot of times, so maybe not. I also sprayed carb cleaner thru most of the openings in the carb and according to this article, maybe I shouldn't have. I didn't have a rebuild kit to install at the time.

The diaphragm is a bit puckered, but the saw is pumping lots of fuel, so I don't think that's the main problem.

Put it back together and saw runs the same - starts right away, runs at high idle speed, won't rev up, gas is leaking out muffler as saw runs.

Does this sound like a bad check valve? Bad needle valve or height? Something else?

Any suggestions are appreciated.

Also does anyone know which rebuild kit this saw takes? or an inexpensive source for a new carb?
I'm trying not to buy a new carb

Check the welch plug, may be loose or leaking. I've had several saws exhibit this type of problem and fixed them by sealing the welch plug. Take a pick, dip it in fingernail polish, and run it around the edge of the plug. I like to use the wife's white polish, easy to see what you're doing. A little goes a long way.

I would start with a good cleaning and then a kit. Diaphragms do get old and stiff and will not deflect the metering arm correctly, and the flaps will not flutter correctly on the pumping side.

I use carb cleaner, shot through straws, on carbs that are getting routine rebuilds before I sell the saw. I have not had a problem result from using this method. If the saw was not running right before I pulled it apart, I use a good soak in the USC. If you haven't haven't changed anything inside the carb, it is unlikely the metering arm is the problem. The arm should be set at the height of the carb body. I did find in the Zama info that the arm could be set a bit below the body level. Sometimes a saw will idle down but eventually die. Lowering the metering arm a bit will often clear this up.

kr5258 said:

Check the welch plug, may be loose or leaking. I've had several saws exhibit this type of problem and fixed them by sealing the welch plug. Take a pick, dip it in fingernail polish, and run it around the edge of the plug. I like to use the wife's white polish, easy to see what you're doing. A little goes a long way.

Click to expand...

Thanks very much!
I didn't take the welch plug out, but when I was spraying carb cleaner in that vicinity something kind of popped back up, but I couldn't tell what it was - maybe it was the seal on the welch plug giving up.

nmurph said:

I would start with a good cleaning and then a kit. I use carb cleaner, shot through straws on carbs that are getting routine rebuilds before I sell the saw. If the saw was not running right before I pulled it apart I use the USC. I have not had a problem result from using this method. You might also tinker with the metering arm height. Sometimes a saw will idle down but eventually die. Lowering the metering arma a bit will often clear this up. However, if you haven't been inside the carb, it is unlikely the metering arm is the problem. Diaphragms do get old and stiff and will not deflect the metering arm correctly, and the flaps will not flutter correctly on the pumping side.

Click to expand...

Thanks nmurph.

dboyd351 said:

Thanks nmurph.

Click to expand...

Re-read my post. I edited it to add some info and to make it more clear. It is a bit early and my mind is still waking up.

I'd look at the welch plug too, it seems a perennial weakness of the C1Q.

Also, this is a strato saw (GZ400) - is the air valve opening properly? Without the air valve, these carbs are very small for the displacement an the mixture will likely get very rich.

WoodHeatWarrior said:

I'd look at the welch plug too, it seems a perennial weakness of the C1Q.

Also, this is a strato saw (GZ400) - is the air valve opening properly? Without the air valve, these carbs are very small for the displacement an the mixture will likely get very rich.

Click to expand...

WHW,
Yes, the air valve is opening as it should. I had that problem on another one, so I knew to check for that. I'm thinking the welch plug is the answer, since I definitely noticed it kind of "pop" when spraying that area with carb cleaner. Should have realized that was probably the sealant giving up, but I've never screwed with the welch plugs and I didn't realize what had happened. If you look at the carb rebuild video from eReplacement parts, specifically for Zama carbs, they show they spraying the whole carb liberally with cleaner and don't mention anything about the welch plug needing to be re-sealed.

Learn something new every day.

dboyd351 said:

WHW,
Yes, the air valve is opening as it should. I had that problem on another one, so I knew to check for that. I'm thinking the welch plug is the answer, since I definitely noticed it kind of "pop" when spraying that area with carb cleaner. Should have realized that was probably the sealant giving up, but I've never screwed with the welch plugs and I didn't realize what had happened. If you look at the carb rebuild video from eReplacement parts, specifically for Zama carbs, they show they spraying the whole carb liberally with cleaner and don't mention anything about the welch plug needing to be re-sealed.

Learn something new every day.

Click to expand...

I really don't like C1Q's, mainly because of that odd shaped welch plug.

Thanks to KR5258, nmurph and WHW for the advice.
The saw is now rebuilt and running again.
Revving, idling, etc. I think the welch plug was the trick, but while I was in there I went ahead and rebuilt the rest of the carb with new parts.
Thanks greatly for the advice, especially about the welch plug.

David

maico490 said:

This has been my first experience with the notorious check valves found on newer carbs. I've been chasing this problem on a FS450 trimmer for a while but luckily it has been between cuts on Water Authority sites. Searching here didn't throw up much but these carbs are used on lots of blowers, trimmers and smaller saws. The carb is a Zama C1Q-S34H which is fixed jet with only what appears to be an air screw (reverse thread) for idle adjustment.Symptoms were hard starting, inconsistant idle which couldn't be adjusted and would run out of fuel with an inch still left in the tank. When operating the primer bulb you could keep pumping without it becoming full and air bubbles were visible in the bulb. At full throttle everything was fine but as soon as you let off it would often stop dead. New lines, primer bulb,fuel filter and a rebuild kit did nothing. The answer was eventually found on Zama's excellent website: USA Zama : Service Tips.
Before you do anything to a Zama carb I would recommend reading all the Service Tips. Especially DO NOT BLOW COMPRESSED AIR THROUGH A CARB WITH CHECK VALVES. It seems you also have to be careful with aerosol carb cleaner if directed straight into the valve with an extension tube.
So here's how it went:

The jet at the bottom of the metering chamber is the main jet which Zama call the "Nozzle Assembly Check Valve". Stihl call it the "Valve Jet".
The hole in the middle, which is normally hidden by the metering lever leads to the idle circuit. To test both circuits use a piece of hose over the jet and blow with your mouth. If clear then try to suck back. If you can the check valve is defective. This is bad news on the idle circuit as it means a new carb but the main jet can be replaced. Zama do a special tool but I managed to use a cheap drill press and one of my extensive collection of broken drill bits. If you have adjusting screws remove the H before starting.

It took a fair bit of fiddling to get everthing lined up and more force than I expected to get the nozzle to move. Here it is out and the new one:

The new one went in a lot more easily:

A few minutes of reassembly and it fired right up. Ticks over fine now and is responsive to the LA screw.

Click to expand...

Great thread!:msp_thumbup: Thanks for sharing, this is going to save me a lot of grief in the future...